372
FXUS63 KARX 031518
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
918 AM CST Wed Dec 3 2025

.KEY MESSAGES...

- Very cold temperatures are expected tonight and into Thursday
  morning with lows falling below zero areawide. Wind chills of
  10 to 25 degrees below zero are expected Thursday morning.
  Highs will likely only reach into the single digits to lower
  teens for Thursday.

- A weak system brings some snow chances (30-55% chance) for Saturday
  and Saturday night. However uncertainty still remains in the
  exact track of this disturbance.

&&

.UPDATE...Today
Issued at 910 AM CST Wed Dec 3 2025

A shortwave trough will move southeast across the area today.
With steep 950-900 mb lapse rates, this trough will produce
widespread flurries across the area. Due to this, the forecast
was updated to increase their coverage.

&&

.DISCUSSION...
Issued at 324 AM CST Wed Dec 3 2025

Today - Thursday: Light Snow Exits, Much Colder Into Thursday

A surface cold frontal passage associated with a large upper-level
trough over Ontario will be the primary synoptic feature that will
dictate our conditions over the next 36-48 hours. Currently, pre-
frontal moisture and weak lift ahead of the cold front has initiated
some pockets of light snow across the area early this morning.
However, given the fast trajectory of the approaching cold front,
much of this should translate east of the local area by daybreak.
Overall accumulations will generally be minimal, on the order of a
trace to 1/2".

The larger story with this passing cold front will be the sharp cold
air advection it will bring along with it. As it passes through the
area this morning, temperatures will drop throughout the afternoon
and evening. As surface high pressure pushes into portions of the
Upper Midwest by the overnight hours, skies will likely clear out
with decreasing winds which will allow for efficient radiational
cooling. As a result, much of the NBM percentiles agree for
temperatures to fall below the 0 degree mark areawide tonight.
Additionally, some wind will remain with a weak surface pressure
gradient in place over the local area as the surface high centering
itself over central IA. Consequently, expecting wind chills by
Thursday morning to fall into the 10 to 25 below zero range, with
the coldest wind chills across unsheltered areas of southeast MN and
northeast IA. Cannot rule out La Crosse even seeing a record cold
low for Thursday morning as their daily record cold low for December
4th is -6F which was set back in 1893. Temperatures will not recover
all that substantially going into the afternoon with highs generally
progged to only reach into the single digits to lower teens above
zero with maximum wind chills still only in the single digits above
and below zero. Needless to say, make sure to wear multiple
layers when heading outdoors on Thursday.

Friday - Early Next Week: Colder Than Normal, Periodic Snow Chances

As we head into Friday, upper-level flow returns to slightly more
zonal allowing for warm air advection to push into the area and
returning highs back into the 20s for much of the local area. By the
weekend, the synoptic setup shows an upper-level trough situated in
Ontario, Canada to our east with our region subjected to quasi-zonal
to northwesterly flow. The main feature to watch will be a shortwave
that descends from western Canada and into the Great Plains during
the day on Saturday and into Saturday night. There still remains
great uncertainty as to where the exact track of this shortwave will
end up as cluster analysis of the grand ensemble (GEFS/EC/Canadian
ensemble) varies greatly. Currently, three scenarios seem to be in
play the first (roughly 20% of members) of which pushes the
shortwave squarely through our area due to the upper-level trough
being weaker with high probabilities (40-70% chance) for
accumulations of an inch or greater. The second and currently most
favored scenario with around 70% of members pushes the wave through
central IA and clips areas west of the Mississippi River with some
probabilities (20-50% chance) for one inch or greater of
accumulations. The last scenario which roughly 10% of members in the
grand ensemble show pushes the shortwave well to our south as the
upper-level trough in Ontario is much stronger and more amplified.
Regardless, very few members have any signal for amounts on the
order of 3" or greater so really not expecting an overly
impactful system, but certainly is our next shot for any
meaningful precipitation.

By next week, northwest flow re-establishes itself with guidance
keeping temperatures still slightly below normal into Monday with
highs likely remaining below the freezing mark. Deterministic
guidance in the GFS/EC/Canadian show various shortwave perturbations
that try to sneak into the area early next week. However, the
resolvability of any of these features remains low at this time. In
any case, would expect at least some periods of precipitation into
next week, but finer details remain unclear at this point.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 525 AM CST Wed Dec 3 2025

MVFR to IFR cigs will be the primary aviation consideration this
morning as low-level stratus maintains across the region. IFR
reductions will likely be short-lived this morning as the recent
HREF probabilities wane for IFR cigs after 15z. Low-level moisture
remains in place somewhat into the afternoon so have kept MVFR cigs
at both TAF sites before eventually the low-levels dry out towards
sunset leaving behind VFR conditions. Cannot rule out (less than
20% chance) some patchy freezing drizzle initially over the
next few hours as RAP/HRRR soundings lose saturation in the
dendritic growth zone, this will be a short-lived window though
as eventually much of the lower levels dry out significantly
which would put an end to any precipitation production. Winds
will be from the northwest at around 10-15 kts throughout much
of the daytime hours and will diminish gradually during the
overnight to around 5 kts or less.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.

&&

$$

UPDATE...Boyne
DISCUSSION...Naylor
AVIATION...Naylor